Laser processing typically involves the use of a laser to perform activities such as cutting, heating, burning, ablation, or the like. In this application, the focus is on laser ablation however; similar principles may apply to other types of laser processing.
Laser ablation is a process that can be used to remove material from a surface/substrate in a controlled manner. In general, the intense laser energy removes the material through various physical processes, and usually results in plasma being ejected in a plume from the substrate. The process can be precisely controlled by varying the properties of the laser in relation to the material's optical properties.
Mask projected laser ablation is a machining process whereby the distribution of laser energy impinging on the surface/substrate consists of a projected image formed by passing laser energy through a negative of the desired pattern (mask). Mask projection laser ablation offers the advantage of allowing a relatively large area of a particular substrate to be machined at one time compared to other laser machining methods, which allow very limited areas to be machined.
FIG. 1 illustrates an exemplary mask projection system configuration. A laser 10 is sent through condensing optics 12 and onto a mask 14, as described. The laser energy passing through the mask 14 and a projection lens 16 produces the desired pattern on a product 18.
Coverage of mask projection systems is generally limited by available laser pulse energy. The nature of ejected material produced during the ablation process, especially the size and composition of solids, has a substantial effect on the cleanliness of the process and indirectly on the quality of the ablated substrate. Controlling the chemistry of the ablated material and efficient removal of debris are important elements of the process. Process gases, such as an assist gas and/or a cover gas or similar, are typically added to the ablation area to facilitate the ablation process. A cover gas typically provides a controlled (typically inert) environment for the process. An assist gas facilitates the process typically by chemical reaction with the material being machined. For the purposes of this application, both will be referred to as “process gas”, since the nozzle is not restricted to the type or purpose of the gas.
A vacuum debris removal system is typically provided to remove ablated material and to provide a controlled environment around the ablated area of the part. However, existing nozzles continue to have problems with regard to debris build-up affecting the laser energy. It is, therefore, desirable to provide an improved laser ablation system.
Although not previously identified, the construction of existing nozzles can cause uneven pressure in the flow of the process gas to the product and in the flow of debris away from the ablation site, potentially having an effect on the quality of debris removal, and on the product itself.